View Full Version : Watt Meter in Flight?

09-13-2005, 08:00 PM
Has anyone connected a Watt Meter to record actual power draw of a motor while in flight? I'm curious because I just tested my Axi 2208/34 and Jeti 08 Plus ESC (with both a 11.1V and 7.4V Lipo) and recorded a maximum 16A draw under load (the plane was stationary under full throttle). The ESC is rated at 8A but I have had no problems in the 2 months I've been flying. The current in flight is probably less than 16A but I'm not sure by how much.



Matt Kirsch
09-19-2005, 05:28 PM
It's probably not a problem because you don't use full throttle much, and have good cooling. You'll have to give up a little power, but I highly recommend that you prop down a little bit to get those Amps more reasonable for the ESC, battery, and motor.

The prop unloads, but nowhere near 50%. It's more like 10-15% and then only on planes that maintain forward motion. If you're doing 3D, figure you're drawing about the same as you did on the bench.

There are onboard telemetry systems out there, but they're relatively hefty and pricey. A regular Wattmeter only shows real-time information, so unless you can fly alongside the plane and look in, it's pretty much useless for in-flight readings.

09-20-2005, 02:17 AM
Thanks. I have a Watt Meter from Powerwerx.com and it does keep the peak amps, peak watts, total Amp-hours, total Watt-hours, and minimum volts on the battery side on screen until you disconnect the power source.


09-25-2005, 05:51 AM
Yep, I have the watts up meter as well and it's great. I bought to use on my large scale gasser to see how many amps my servos pull in a flight. Helps me to determine if I need more battery mah, etc... Should be good on electric as well. Start out at less than full throttle to take off and then do a full throttle level pass to see what it records.

10-07-2005, 12:36 PM
There are also systems that record that information and you download it when you land. It keeps a graph of usage, I believe.

10-09-2005, 04:19 AM
I would say you are pretty lucky so far. Remember that the ESC and motor only see 100% throttle. The problem with watt meters is they only give you an average over a sampling period (usually 1 second for the ones like the Watts up). On your system 50% throttle may show 8a current with one of these meters. But because of the way the ESC works it is actually delivering (and the motor is exposed to) 16A 50% of the time.

When sizing props, motors and ESCs you have to go by WOT current levels. When sizing batteries you can go by the average.

All of the above is for brushless only.

PS Here is the in-flight recorder. http://bnbproducts.com/index.htm About $30 more than a Watts Up.

10-09-2005, 04:29 AM
For me, it's the wot that I worry about. I make sure the wot amps are not beyond my components ability to handle them. You are going to goof and go there sometime anyway.:D